DESCRIPTION (adapted from the Abstract): Tactile object recognition requires shifts of attention to features touched sequentially during exploration and short-term storage of perceived attributes for comparisons with the sensations produced by later manipulations. To understand this process, this Principal Investigator proposes studies to examine which cortical areas and what neural response patterns are related to selected processing of the attributes of touched objects. Findings from these studies may contribute to the design of tactile prostheses and training strategies for rehabilitation. In these experiments humans and monkeys must discriminate the value of one tactile attribute, often in the presence of another attribute, for optimal performance. For Aim #1 the Investigator proposes recording from single cells in primary somatosensory cortex (SI) in monkeys selectively cued to detect different combinations of auditory tone amplitude patterns and concurrent vibrotactile amplitude patterns on the hand or fingers. For Aim #2 he proposes recording from single cells in SI and second somatosensory area (SII) of monkeys selectively cued to one of two simultaneously presented tactile features of a vibratory stimulus. Cues inform monkeys to attend to changes in frequency (e.g., test stimulus higher or lower than standard) or duration (e.g., longer or shorter than standard). For Aim #3 the Investigator proposes a neuroimaging study using Positron Emission Tomography (PET) in humans cued to tactile attributes. Cues inform subjects to attend to changes in frequency or vibration duration as in Aim #2 or to direct attention to changes in surface roughness or surface length. For different scans subjects attend selectively to one cued attribute or divide their attention between two attributes. For Aim #4 the Investigator proposes recording from single neurons in SI and SII of monkeys doing a delayed-matching task that involves learned paired-associations between tactile gratings or between visual and tactile gratings. At issue in this study is whether remembering sample stimuli modulates responses to machining or non-matching tactile stimuli and whether these effects differ for intra-modal and cross-modal information transfers.